6 and 7-bromomethyl pteridines and process of preparing same



Patented Feb. 5, 1952 6 AND 7-BROMOME'1HYL PTERIDINES AND PRQCESS OF PREPARING SAME James H.v Boothe, Bear! River, N. Y., assignor to American Cyanamid Company, New York, N. Y., a corporation of Maine No Drawing. Application June 24, 1948,

Serial No. 35,069

Claims. (01.260-2515) 1 a This invention relates to new organic compounds. More particularly, it relates to bromo pteridines and methods of preparation thereof.

In my application, Serial No. 686,716, filed July 27, 1946, now Patent No. 2,547,519, I describedthe preparation of 6-halomethyl pteridines and the reaction of these compounds with para-aminobenzoylglutamic acid to produce'pteroylglutamic acid. This application, which is a continuation in-part thereof, describes and claims the 6-bromofmethyl pteridines, 6-monobromomethy1 pteridine and 6-dibromomethy1 pteridine, as well as other bromomethyl pteridines. The bromopteridines of the present application may be represented by the formula:

in which R and R are members of the group consisting of hydrogen, methyl, bromomethyl and dibromomethyl radicals, at least one being a bromo methyl radical. Such compounds can be prepared by brominating the corresponding methyl pterifdine under conditions set forth in my application, Serial No. 686,716, and as described in detail hereinafter. w

The compounds of the present invention are generally yellowish to white crystalline "substances, slightly soluble in hot water and soluble in acids and dilute alkali and are relatively insoluble in ether, acetone and alcohols, except in the presence of strong acids. .They are useful as intermediates in the preparation of pteroylglutamic acid and related compounds.

The 6-,methyl and7-methyl pteridines used as intermediates in the present process are prepared by methods described in a co-pending application of John H. Mowat, Serial No. 633,870, filed,December 8, 1945, now Patent No. 2,443,078;

The compounds of the present invention are prepared by heating the corresponding 6 or 7- methyl pteridine or6,7-dimethyl pteridine with bromine in the presence of a suitable solvent such as concentrated hydrobromic acid, ethyleneglycol, trichloroacetic acid and the like. Asdescribed in the co-pending application, the product first obtained on bromination of G-mthyl pteridine with an excess of bromine is a mixture of the monoand di-bromomethyl pteridine.- .The dibromomethyl pteridine is less soluble thanthe monobromomethyl pteridine and on concentrating a solution containing both, the dibromo compound will separate out first. In brominating the 7-methyl pteridine with an equivalent amount of bromine the 7-monobromomethyl pteridine is obtained whereas with an excess of bromine the dibromomethyl pteridine is predominant.

The reaction of the present invention is preferably carried out at a temperature of from about C. to 150 C. The reaction can be carried out at the lower temperatures. However, for practical purposes it is more desirable to carry out the reaction under refluxing conditions of the particular solvent used. I

Another method of preparing the present com-- .pounds is to react 2,4,5-triamino-fi-hydroxypyrimidine with bromomethyl glyoxal, dibromodiacetyl, tetrabromodiacetyl and the like. This method depends on the formation of the pteridine ring having the bromomethyl radical in the desired position.

0n crystallizing the compounds of the present invention from strong acids, such as concentrated hydrobromic acid, the corresponding acid salt separates from solution. However, if a strong acid solution of the compound is diluted with water, ethanol, methanol, etc. the free base is obtained.

'To illustrate the invention with greater detail, reference is made to the following specific examples in which various 6 or 7-bromomethyl pteridines or 6,7-.-bromodimethyl pteridines are prepared.

Example 1 A mixture of 12 g. of 2-amino-4-hydroxy-6- methylpteridine, 400 cc. of 48% hydrobromic acid solution and 12 cc. of bromine are heated on a steam bath overnight. This bromination mixture with the excess bromine present is then chilled overnight. Some of the brominated product separates as brown cubes which appear to be a bromine complex of the brominated pterin. These crystals are isolated mechanically and crystallized from 48% hydrobromic acid'by running therein a current of air-bromine mixture. As the bromine concentration becomes suflicient, the product separates as brown cubes, but where a large excess of bromine is present the product separated as yellow needles. The crystalline product is collected and washed with 48% hydrobromic acid, which changes the yellow needles to brown cubes. The brown cubes are crystallized twice from hot glacial acetic acid (which contained from 1 to 5% hydrogen bromide) by cooling to give a white crystalline solid with the excess bromine which formed the bromine complex remaining in the solvent. The product on analysis A mlxture'of 50 gnof 2-arnino-4-hydroxy-6 methylpteridine, 50 cc. of bromine and 1500 cc. of

48% hydrobromic acid is heated on the steam bath for 20 hours. The solution obtained i s concentrated to 500 cc. under reduced pressure and at steam bath temperature. The concentrated solution is chilled at -5 C. overnight, Avery;

small amount of crystalline material 1115s.). I

separates which is removed by filtration. The filtrate is treated with activated charcoal and con: centrated to about 350 cc. oughly a crystalline material is isolated, washed with 48% hydrobromic acid, acetone and ether;

weight 20 g. By evaporation and cooling 2. secnd crop of 18 g, is obtained. This material on analysis proved. to be 2-amino-4-hydroxy-6 -dh brqmomethylpteridine hydrobromide.

7 Example 3 The finalfiltrate obtained'in the above example is evaporated to dryness. The residue obtained issuspended in a liter of .cold water, shaken, collected, washed with water, alcohol and ether and dried. A yieldof 27 g. of pterin is obtained which is predominately fi-monobromomethyl pteridine.

This product, when reacted with para-aminobenzoylglutamic acid under suitable conditions, produced pteroylglutamic acid in from 9% to 27 pure material. v 7

Example 4 To 11iter of48% hydr bromi i sta d 2 g. of 2-amino-4-hydroxy-B-methylpteridine and 12 cc. of .bromine and the mixture refluxed for 1 hour to afiect solution and to complete the bromination. This solution is concentrated to 500 cc. under reduced pressure. The concentrated solution is treated with 21 g. of activated char coal, filtered, and run into 3 /2 liters of. cold water. The diluted aqueous solution is neutralized with enough sodium acetate to bring the pH to3 to 5. The product is predominately 2-amino-4-hydroxy-6-dibromomethylpteridine. Weight 24 g.

' Example Example 6 A. mixture of 100 g. of 2-amino-4-hydroxy-7 methylpteridine and 1500 cc. of 48% hydrobromic acid is heated for 20 minutes on the steam bath, and'then to this hot mixture is added a solutionof 100 g. of bromine in'2 00 cc. of 48% hydrobromic acid throughi'a dropping funnel in' a very fine stream. The mixture becomes a clear solution when about half of the bromine-'hydrobromic acid is added. After completing the addition of Aftel cool .V

4 the bromine the solution is heated for minutes more, concentrated to one liter, chilled overnight, concentrated to 500 cc., treated with 50 g. of activated charcoal, filtered, cooled at --5 C. a second time overnight, and filtered. This isolated productis recrystallized twice from 48 hydrobromic acid; slurried infethanolg" collectejdfwashed with ethanol and ether, and dried. The analysis of this material for carbon, hydrogen, nitrogen and 2eamino -4 -hydroxy-7-brornomethylpteridine.

bromine agreed with the theoretical values for Example 7 A solution" of, 40g. of 2-amino-4-hydroxy-7- methylp teridinein' 1200 cc. of 48% of hydrobromic acidis prepared by heating to 70-95 C.

Aftermost 'of'the pterin dissolves, 40 cc. of bromine is added, and the solution heated on the steam bath for 2 hours. This solution is concentrated to 1 liter, treated with charcoal and filtered. The filtrate is seeded and cooled. for several hours. The crystalline 2 -amino-4-hydroxy-7-dibromomethylpteridine' (47.7 g.) is 'colf' lected, washed-With 48% hydrobrofmic acid and Example 8' 2 of 2-amino-4-hydroxy-'I-methylpteridlne is dissolved in 40 cc. o'f 4 8% 'hydrobro nicacidcon taining 4.0 g. of bromine. Thisis heated just under reflux] temperature for 45 minutes and then 5 cc. of the solution is evaporated oft under vacuum to remove excess bromine. After cooling overnight the resulting white crystallinecom pound is' collected on a funnel and washed with a 48% hydrobromic acid solution. This is transferred to a flask and suspended in water containing several drops of pyridine. The crystalline material which is the hydrobromide salt immediately changes to an amorphous yellow solid. The solid is filtered off, washed with water, methanol and ether and dried; A yield of 2.3 g. of product is obtained which analyzed for carbon; hydrogen, nitrogen and bromine agrees with the theoretical valuesfor 2-amino-4-hydroxy '7-dibromomethylpteridine.

That the two bromines are on the 7 -methyl group of the pteridine is shown by the two following experiments:' (1) A- sample of the compound can be reduced using hydriodic acid in glacial acetic acid to give a 60% yield of pure 2 -amino-4- hydroXy-7-methylpteridine; (2) A sample 0f the compound. can be oxidized with alkaline perman= ganate solution to give an %'yield of -2-amino-' 4-hydroxypteridine-'Z-carboxylic acid;

Example 9 To 5 g. of .2-amino-4-hydroxy-6,7-dimethyl pteridine stirred with '250 'cc. of 48% hydrobromic acid and heated to is added all at once 1.34 cc. of bromine in 10 cc. 48% hydrobromic acid. The dimethyl pteringoes' into solution in a few minutes and'the bromine color disappears rapidly. After 10 minutes the solution is cooled in ice 1 hour and the crystalline precipitat -fil= tered ofi, washed and dried. A yield of '3.5'g. of 2-amino-4-hydroxy-fi-methyl l bromomethyl pteridine isobtained;

Erample 1.0

To 1.07 g. of 2,4,5-triamino-G-hydroxypyrimidine dihydrochloride' dissolved in" 25 cc. of 2.5"}? hydrobromio acid isadded 1.22 g. of d'ibromodi acetyl in 10 00.01 alcohol. After one hour at room temperature the; solution is leftlin the chill room 2,se4,sse

overnight. The solution is filtered from a small amount of crystalline material and the filtrate diluted with 100 cc. of cold water. After cooling 6 hours in ice the crystalline product is filtered oif, washed with water, acetone and ether and dried, weight 0.9 g. This material on analysis for carbon, hydrogen, nitrogen and bromine closely agreed with the theoretical values for 6,7-dibromodimethylpterin.

Ercample 11 To g. of 6,7-dibromodimethylpterin dissolved in 210 cc. of 48% hydrobromic acid is added Water to give 750 cc. of solution (2.5 N hydrobromic acid). The solution is warmed to 55 C. and stirred while dropping in 7.13 g. K1 in cc. water over one hour. An iodine color slowly develops. The solution is kept at 55 C. one hour more and then cooled to 15 C. Sodium hydrosulfite is added until the dark iodine color is discharged and most of the black precipitate redissolves. The solution is filtered and neutralized to pH 1 with a saturated sodium acetate solution. The precipitate is filtered off, washed, and dried. A yield of 12.1 g. of product is obtained which is predominately 2 amino 4 hydroxy 6 bromomethyl- 7-methyl pteridine.

Example 12 200 mg. of 2-amino-4-hydroxy-6-methylpteridine is dissolved in a mixture of 7.5 cc. of ethylene glycol and 0.5 cc. of 48% (aqueous) hydrobromic acid at about 50 C. To this solution is added 250 mg. of bromine and the resulting solution warmed for about minutes (at -70 C.).

pteroylglutamic acid as shown by bioassay using S. faecalis R.

I claim:

1. Compounds having the general formula:

in which R and R are members of the group consisting of hydrogen, methyl, bromomethyl and dibromomethyl radicals, at least one of which is a bromomethyl radical.

2. Compounds having the general formula:

OH KIN B NIH-L in which R is a bromomethyl radical.

This solution of the brominated methyl pteridine is mixed 3. 2 amino 4 hydroxy 6 bromomethyl pteridine.

4. 2 amino 4 hydroxy 6 dibromomethyl pteridine.

5. 2 amino 4 hydroxy 7 bromomethyl pteridine.

6. A method of preparing compounds having the formula:

on LI/EjNIR N Hg-\N N R v in which R and R are members of the group consisting of hydrogen, methyl, bromomethyl and dibromoinethyl radicals, at least one of which is a bromomethyl radical, which comprises heating a compound having the formula:

in which R is a bromomethyl radical which comprises heating 2 amino 4 hydroxy 6 methyl pteridine with bromine in the presence of strong aqueous hydrobromic acid and recovering said 6- bromomethyl pteridine therefrom.

3. A method of preparing 2-amino-4-hydroxy- G-bromomethyl pteridine which comprises heating 2-amino-4-hydroxy6-methyl pteridine with bromine and about 48% hydrobromic acid and recovering said 2-amino-4-hydroxy-6-bromomethyl pteridine.

9. A method of preparing 2-amino-4-hydroxy- G-dibromomethyl pteridine which comprises heating 2-amino-4-hydroxy-6-methyl pteridine with bromine and about 43% hydrobromic acid and recovering said 2-amino-4-hydroxy-6-dibromo methyl pteridine.

10. A method of preparing 2-amino-4-hydroxyi-bromomethyl pteridine which comprises heating 2-amino-4-hydroxy-7-methyl pteridine with bro mine and about 48% hydrobromic acid and re- 00 covering said 2-amino-4-hydroxy-7-bromomethyl pteridine.

JAMES H. BOOTHE.

No references cited. 

1. COMPOUNDS HAVING THE GENERAL FORMULA:
 6. A METHOD OF PREPARING COMPOUNDS HAVING THE FORMULA: 